It has to have a good purpose. Obviously there are a lot of words written about what constitutes a good purpose. Antivirus is probably one. Wanting to intimidate your employees is not. The same thing applies to security cameras.

Privacy laws are about the end-to-end process, not technical implementation. It's not "You can't MITM TLS" - it's more like "You can't spy on your employees". Blocking viruses is not spying on your employees. If you take the logs from the virus blocker and use them to spy on your employees, then you are spying on your employees. (Virus blockers aiming to be sold in the EU would do well not to keep unnecessary logs that could be used to spy on employees.)